Roller skate



FIG. 1 is a perspective view of a roller skate taken from the right front and showing my new design;

FIG. 2 is a right-side elevational view thereof, the left side being substantially a mirror image thereof, except for the uppermost portion which is shown in FIG. 1;

FIG. 3 is a rear elevational view thereof; and

FIG. 4 is a bottom plan view thereof. 

The ornamental design for a roller skate, as shown and described. 